Related Experiment Video
Updated: Sep 5, 2025
13:21
Preparation, Purification, and Characterization of Lanthanide Complexes for Use as Contrast Agents for Magnetic Resonance Imaging
Published on: July 21, 2011
15.1K
Lanthanide Complexes (GdIII and EuIII ) Based on a DOTA-TEMPO Platform for Redox Monitoring via Relaxivity
Richard Barré1, Damien Mouchel Dit Leguerrier1, Quentin Ruet2,3
1Univ. Grenoble Alpes, CNRS, DCM, 38000, Grenoble, France.
Chemistry, an Asian Journal
|July 7, 2022
Summary
New redox-active lanthanide complexes were synthesized for potential MRI contrast agents. These gadolinium (Gd) and europium (Eu) complexes show tunable relaxivity and low toxicity, with one complex exhibiting cell penetration.
Area of Science:
- Coordination Chemistry
- Materials Science
- Biomedical Imaging
Background:
- Development of novel contrast agents for Magnetic Resonance Imaging (MRI) is crucial for enhanced diagnostic capabilities.
- Lanthanide complexes are widely explored due to their paramagnetic properties, particularly Gd(III) for relaxivity and Eu(III) for luminescence.
- Incorporating redox-active moieties can introduce additional functionalities and responsiveness to lanthanide complexes.
Purpose of the Study:
- To synthesize and characterize novel lanthanide complexes featuring a redox-active TEMPO-based arm.
- To investigate the redox behavior and coordination properties of these new complexes.
- To evaluate their potential as MRI contrast agents by measuring relaxivity and assessing cellular toxicity and uptake.
Main Methods:
- Synthesis of three lanthanide complexes (Gd, Eu) based on DO3A or DO2A platforms with a TEMPO-arm.
- Post-functionalization of an alkyne-containing complex using click chemistry.
- Characterization using luminescence spectroscopy, fast-field cycling NMR relaxometry, and Electron Paramagnetic Resonance (EPR) spectroscopy.
Main Results:
- The synthesized complexes exhibit tunable redox states (hydroxylamine, nitroxide, oxoammonium) of the TEMPO arm.
- Luminescence studies confirm octadentate or heptadentate chelation by the ligand, with a coordinated water molecule.
- Gd(III) complexes display promising relaxivity (r1) values that increase upon oxidation of the TEMPO arm, with no observed toxicity up to 40 μM in M21 cell lines. EPR indicates limited cell penetration, except for [Eu(L2)]+.
Conclusions:
- The study successfully prepared redox-active lanthanide complexes with tunable properties.
- These complexes demonstrate potential as responsive MRI contrast agents with low toxicity.
- Differential cell penetration was observed, highlighting the influence of complex structure on cellular interactions.
Related Concept Videos
00:43Complexometric Titration: Ligands
1.1K
Different monodentate and polydentate ligands are used as complexing agents in complexometric titration reactions. The formation of complexes by mono- and bidentate ligands involves two or more intermediate steps, limiting their use as complexing agents. In comparison, polydentate ligands can form complexes with metal ions in a single-step process, facilitating sharper end points. This means polydentate ligands, such as amino carboxylic acid derivatives, are most commonly employed in...
1.1K
03:02Colors and Magnetism
12.3K
Color in Coordination Complexes
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human...
12.3K
00:39Complexometric Titration: Overview
7.6K
Complexometric titration involves the formation of a complex by reacting a metal ion with one or more ligands. A visual indicator often detects the end point of a complexometric titration. It is added to the metal solution before the titration, forming a stable metal–indicator complex and imparting color to the solution. As the titration approaches the equivalence point, the excess of the added ligand displaces the indicator from the metal–indicator complex, releasing the free...
7.6K
01:26Redox Titration: Other Oxidizing and Reducing Agents
384
Besides iodine, other oxidizing or reducing agents can serve as titrants in redox titrations. Common oxidizing titrants include KMnO4, cerium(IV), and K2Cr2O7. The choice of oxidizing titrants depends on factors like stability, cost, analyte strength, and reaction rate between the analyte and titrant. KMnO4 is a strong oxidizing titrant that reduces from Mn(VII) to Mn(II) in a highly acidic solution, simultaneously oxidizing the analyte to a higher oxidation state. In this case, KMnO4 acts as a...
384
01:22EDTA: Chemistry and Properties
2.2K
Polydentate ligands are most widely used in complexometric titrations because they form more stable complexes with the metal ions than mono- or bidentate ligands due to the chelate effect. Examples of polydentate ligands are ethylenediaminetetraacetic acid (EDTA), crown ethers, and cryptands. The most important feature of optimal polydentate ligands is the ability to form 1:1 complexes in a single-step process. Amino carboxylic acid derivatives are frequently used as complexing agents. EDTA is...
2.2K
01:21Redox Titration: Overview
3.4K
Redox titration is a chemical analysis technique used to determine the concentration of an unknown substance by measuring the electron transfer in a redox (reduction-oxidation) reaction. The process involves gradually adding a titrant with a known concentration of an oxidizing or reducing agent, to the analyte, the solution with an unknown concentration, until reaching the endpoint, which indicates the completion of the reaction between the two substances. Ensuring the analyte is in a single...
3.4K